1. Field of the Invention
This invention relates to a data recording/reproducing apparatus using a disklike recording medium such as a magnetic disk, and more particularly to a data recording/reproducing apparatus capable of performing high density recording by effectively reducing the interference between tracks due to the non-repeatable vibration of a spindle motor employed therein.
2. Description of the Related Art
Magnetic disk apparatuses, and in particular hard disk apparatuses are sold with tracks formed on their disks as a result of magnetically recording servo information thereon. To form such tracks in each apparatus as a semi-finished product, a magnetic head installed therein is moved over a magnetic disk mounted on a spindle motor, and is positioned on a certain point on the disk, thereby recording head-positioning information called "servo information" in the form of tracks. The process for recording servo information on a magnetic disk will be referred to as "servo track writing".
In such a servo track write method for forming tracks on a magnetic disk, as the density of tracks is increased so as to increase the recording capacity, adjacent tracks will interfere with each other, i.e. intersect with each other because of vibration of the spindle motor called "non-repeatable vibration". The "non-repeatable vibration" is mainly caused by the movement of balls contained in the ball bearing of the spindle motor, which is called "rolling element vibration". It is known that a minimum frequency component contained in the "rolling element vibration" is due to revolution of balls. For example, it corresponds to a vibration component with a low frequency of about 30 Hz! and a very large amplitude indicated by the arrow in FIG. 4. This vibration component will occur because of unevenness in size between the balls and often has the largest amplitude among all frequency components of the non-repeatable vibration, as is shown in FIG. 4. The vibration component may well cause the aforementioned interference between adjacent tracks at the time of servo track writing, and hence be a serious obstacle in increasing the density of tracks.